Should 'The Hobbit' Include Saruman?

Once Guillermo del Toro signed on for The Hobbit, all the rest of the buzz began. It sounded great when the filmmaker said he wanted to bring The Lord of the Rings cast back, and when word came that some of them had begun talks. But what about the folks who were in the Rings, but not The Hobbit? Like, say, Christopher Lee'sSaruman?

Empire talked with the 86-year-old actor recently, and he said: "I'd be interested in seeing how that transition from good to evil occurred and, yes, of course I would return to the role if I was asked." Well, he said a little more than that. See, Lee is a pretty big fan of the books and says that he's read them many times. He discussed the intricacies of the wizards, and how "When it all started, Saruman was the noblest, the finest, the bravest, the most dependable and reliable of them all, he was number one. But somewhere, somehow..."

This all brings up an interesting point: Adding characters to other works can be questionable, especially prequels they aren't mentioned in, but what if the character has a back story/mystery that is perfect for the big screen? Is it okay for filmmakers to explore this territory, or should works be adapted only with the characters between the covers?